Liang Cheng, MD
Mortality from TC has been decreasing since the 1970s due to cisplatin-based chemotherapy regimens2,3; TC is among the most curable of solid neoplasms, with a 5-year relative survival rate of 95%.2-4 Thus, the focus of research has shifted from optimizing treatments for improved survival to decreasing treatment-related, long-term adverse events (AEs).5
New Modifications in Risk Assessment and Prognostication
The widely accepted risk stratification model in use today was first developed in 1997 by the International Germ Cell Cancer Collaborative Group (IGCCCG) after studying data on patients with seminoma and NSGCTs.6 The original classification categorized metastatic NSGCTs as having good, intermediate, or poor prognosis based on levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), lactate dehydrogenase (LDH), and the presence of nonpulmonary visceral metastases (NPVM). Primary mediastinal NSGCTs were classified as having poor prognosis regardless of the other factors.6 Metastatic seminoma GCTs were categorized as having good or intermediate prognosis based on the occurrence of brain, liver, or bone metastasis.7
Using contemporary data from more than 12,000 patients with metastatic GCTs who received either cisplatin or etoposide, the IGCCCG model was updated in 2021. For seminoma GCTs, 5-year progression-free survival (PFS) and 5-year overall survival (OS) were extended for both good and intermediate prognostic groups.7 LDH remained the most significant prognostic factor for determining good prognosis however, patients with LDH above 2.5× upper limit of normal (ULN) before chemotherapy had worse survival probabilities than patients with LDH at 2.5× ULN or lower. The survival probabilities for patients with otherwise good prognosis with LDH of more than 2.5× ULN were like those for patients with intermediate prognosis.7 Thus, using LDH of more than 2.5× ULN has revealed a subgroup with significantly worse outcomes within the “good” prognostic group.7,8
For NSGCTs, 5-year PFS rates did not differ from the original IGCCCG for good and intermediate prognostic groups; however, the 2021 update revealed an improved PFS for the poor prognostic group. The 2021 update also demonstrated that 5-year OS rates improved for each group, and further confirmed that the 2 most important prognostic factors for NSGCT were the presence of NPVM and the presence of a mediastinal primary tumor. The update added 2 new adverse prognostic variables: age and metastases. Risk of progression increases 25% with every decade-of-life increase, and 66% with the presence of lung metastases. The LDH groups were reduced to a single cutoff at 2.5× ULN for NSGCTs.8
Primary and Subsequent Treatments for TC
Guideline-directed first-line and subsequent treatments for seminomas and NSGCTs have been developed by several organizations, including the National Comprehensive Cancer Network, IGCCCG, and the American Urological Association (see Figure 1 and 2). An analysis of the most used treatments was performed using the National Cancer Database.2 Most patients underwent orchiectomy without chemotherapy or radiation for both stage I seminomas (78%) and NSGCTs (57%). For stage II and III seminomas, most patients underwent surgery with chemotherapy (66% and 68%, respectively). Nearly half of patients with stage II NSGCTs were treated with surgery and chemotherapy (49%), and a third were treated with retroperitoneal lymph node dissection (RPLND) in addition to surgery and chemotherapy. Surgery with chemotherapy was used for 55% of stage III NSGCTs; other treatments included surgery combined with chemotherapy and RPLND (19%), and chemotherapy with or without radiation (20%).2 However, nearly 30% of patients with TC do not receive guideline-directed therapy, including inappropriate imaging and overtreatment; and nonguideline–directed therapy has been independently associated with risk of relapse.12,13
Figure 1. First-line and Subsequent Treatment of Seminomas
Figure 2. First-line and Subsequent Treatment of Non-Seminomas
TC Survivorship
The trend of improved OS after treatment for metastatic GCTs highlights a need to focus on survivorship. The 10-year survival rate for TC post-treatment is 95%.14 Latest estimates suggest there are more than 300,000 TC survivors in the United States,2 accounting for approximately 4% of all US male cancer survivors.14 With longer-term survival, however, comes the risk for long-term complications from cancer treatments. For example, circulating platinum has been detected in the plasma of men up to 28 years after undergoing cisplatin-based chemotherapy for TC.15 Increasing levels of residual serum platinum have also been shown to correlate with severity of neurotoxicity between 5 and 20 years after treatment.16
A significant concern with cancer treatment is the development of second malignant neoplasms (SMNs).14,17 The relative risk of the development of SMNs depends on whetherradiation therapy or chemotherapy, or both, was used as the primary treatment. Patients who received either radiation therapy or chemotherapy are at increased risk for leukemia and solid cancers, including gastrointestinal cancers. For patients treated with cisplatin, a significant dose-response relationship between cumulative dose and leukemic risk has been reported.14
Other concerns are increased non-TC mortality and SMN mortality. Hellesnes et al examined cause-specific, non-TC mortality using a population-based cohort in Norway.18 They determined that the overall 25-year, non-TC mortality risk was 13.7% (95% CI, 12.5-14.9) for patients who previously had TC vs 11.3% for patients who never had TC. The highest mortality rates were reported for patients who had radiation (19%) or platinum-based chemotherapy plus radiation (18.4%); the lowest mortality rate was reported for patients who had received platinum-based chemotherapy only (9.5%). Patients with the highest non-TC mortality risk were fewer than 20 years post-cancer diagnosis. Non-TC mortality excess ranged from 23% to 40% for patients with a prior TC diagnosis, and a significant 1.43- to 3.24-fold increase in SMN mortality emerged after treatment with platinum-based chemotherapy or radiation therapy, or both.19 Awareness of the increased premature mortality risk is crucial for both TC survivors and their care providers.18
Quality of life for TC survivors appears to be affected by the presence of long-term treatment-related AEs.18 The relative risk of developing cardiovascular disease increases after treatment with chemotherapy. Raynaud phenomenon resulting from bleomycin-induced vascular damage developed within 4 to 12 months after chemotherapy for 18.7% to 39% of TC survivors.14,19 Bleomycin may also cause pulmonary toxicity. Pulmonary surgery, tobacco use of ≥ 20 pack-years, and a cumulative cisplatin dose of > 850 mg are risk factors for late bleomycin-associated pulmonary toxicity.14
Other late-developing toxicities resulting from cisplatin treatment include ototoxicity, neurotoxicity, nephrotoxicity, chronic fatigue, and hypogonadism.14,19 Nearly 1 in 5 North American survivors treated with cisplatin reported severe-to-profound hearing loss within a median of 4.3 years. The extent of hearing loss has been directly associated with the increase in cumulative cisplatin dose. Peripheral neurotoxicity after cisplatin-based chemotherapy is reported to be as high as 40%.14 Chronic cancer-related fatigue can range from 15% to 27%, and has been associated with peripheral neuropathy, low testosterone levels, low physical activity, anxiety, and depression. Post-treatment hypogonadism ranges from 11% to 16%.14,17,20,21
Psychosocial issues are also of concern. Mild-to-moderate psychological distress with diagnosis and survivorship has been reported.17 Anxiety and depression are higher in TC survivors than in the general population. Variables associated with clinically significant anxiety include younger age and shorter time from diagnosis; whereas feeling helpless/hopeless, having less social support, having a higher number of physical symptoms, and having children are factors associated with higher levels of depression. A moderate-to-high level of fear of recurrence has also been reported.17
Recent Clinical Trials in Stage II Disease
Stage II disease has been the focus of current research to reduce treatment-related toxicities and limit longer-term complications. While few phase 3 clinical trials are ongoing (see Table), the results of several phase 2 trials have been reported recently.22-24
Table. Ongoing Interventional Phase 3 Clinical Trials Involving Testicular Cancer
PRIMETEST was a single-arm, single-center, phase 2 study examining the efficacy and surgical safety of primary RPLND for stage II disease.22 Participants underwent either open or robot-assisted unilateral RPLND for stage IIA or B seminoma. No adjuvant treatment was permitted. Of the 33 participants, 9 presented initially with clinical stage II disease (27%) and 24 (73%) had recurrence during active surveillance. Five of the 24 had 1 cycle of carboplatin prior to progressing to stage II. With a median follow-up of 32 months, the study did not meet its primary endpoint of PFS at 36 months. After 32 months, 10 recurrences (30%) were detected, yielding a PFS rate of 70%. All 10 patients with recurrence received chemotherapy and were alive without evidence of disease at the time of publication. This study demonstrates that RPLND may be appropriate for select patients; however, criteria for selecting patients to receive only RPLND need to be clearly defined.22
The SEMS (surgery in early metastatic seminoma) trial was a single-arm, international, phase 2 study of RPLND as first-line treatment for early metastatic seminoma with isolated retroperitoneal lymphadenopathy between 1 and 3 cm (stage II).23 With a median follow-up of 24 months, OS was 100% and 2-year recurrence-free survival was 87%. Recurrence rate was 18% (10 recurrences) with a median time to recurrence of 8 months. Short-term complications occurred in 7 patients (13%), and no patients reported long-term complications. The authors suggested that RPLND is a therapeutic option for first-line treatment in early metastatic seminoma.23
SAKK 01/10 was a single-arm, international, phase 2 study examining the de-escalation of treatment to potentially avoid toxic effects for patients with either stage IIA or stage IIB seminoma.24 Treatment included carboplatin (area under the curve [AUC] 7 mg/mL/min) followed 3 weeks later with involvednode radiotherapy (30 Gy in 15 fractions for stage IIA and 36 Gy in 18 fractions for stage IIB). The study did not meet its primary endpoint of PFS of 95% at 3 years. Grade ≥ 3 treatment-related AEs (TRAEs) included neutropenia (4%), thrombocytopenia (3%), and vomiting (1%). No treatment-related deaths and no late TRAEs were reported. One case of transient creatinine increase was reported as a serious AE, and second primary tumors were reported in 4 participants. Although the primary endpoint was not met, long-term AEs continue to be recorded for potentially up to 20 years. The favorable efficacy and toxicity profile observed in the deescalation combination treatment warrants further study.24
Emerging Trends and Future Directions for TC Treatment
Although the outlook for most newly diagnosed patients with TC is promising, especially for those diagnosed with early-stage disease and good prognosis advanced disease, treatment challenges remain. Between 10% and 20% of patients will have a relapse of TC after initially achieving a complete remission. Most patients will have a relapse within 2 years of initial treatment, but a small subgroup will have a relapse more than 5 years after therapy. Most recurrences occur in the retroperitoneum and lungs and require definitive therapy using chemotherapy and surgical resection.21
Patients with platinum-refractory disease may still achiev long-term remission with salvage therapy of surgery, conventional-dose chemotherapy, or high-dose chemotherapy with autologous stem cell transplantation; however, these treatments will fail for some patients, resulting in poor prognosis. Targeted therapy for TC has not produced meaningful benefits for this population with refractory disease, and the optimal treatment for this group of patients with TC remains to be determined.21
Although current guidelines recommend determining the levels of AFP, hCG, and LDH for clinical staging, treatment monitoring, and follow-up, limitations exist with their usage.9 The assays for these markers have low sensitivity and lack specificity; about half of all GCTs express only 1 of the 3 biomarkers, and seminomas lack AFP expression.7,25,26 Further research is needed on LDH. An emerging group of patients with LDH below 2.5× ULN may be candidates for de-escalatio strategies to reduce treatment burden, while inferior outcomes remain for patients with either good prognosis seminoma and elevated LDH, or intermediate prognosis seminoma.7
Other biomarkers, such as miRNA371a-3p and PD-L1, are being investigated; miRNA371a-3p has been shown to have prognostic significance. The results of this assay can be informative for both seminomas and NSGCTs.26 However, the protocol for quantification and implementation still needs to be determined.27